The role of eptifibatide in patients undergoing percutaneous coronary intervention

Glycoprotein (GP) IIb/IIIa receptor antagonists inhibit the binding of ligands to activated platelet GP IIb/IIIa receptors and, therefore, prevent the formation of platelet thrombi. They have been extensively studied in patients undergoing percutaneous coronary intervention (PCI). Eptifibatide, one of the approved GP IIb/IIIa inhibitors, is a small heptapeptide that is highly selective and rapidly dissociates from its receptor after cessation of therapy. In clinical studies, concomitant administration of eptifibatide in patients undergoing elective PCI reduced thrombotic complications in the IMPACT-II (Integrilin to Minimize Platelet Aggregation and Prevent Coronary Thrombosis II) and ESPRIT (Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy) trials. In the PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) trial, which included 10,948 patients with non-ST-elevation acute coronary syndromes, eptifibatide significantly reduced the primary end point of death and non-fatal myocardial infarction at 30 days compared with placebo. In patients with ST-segment elevation myocardial infarction (STEMI), eptifibatide has been studied as adjunct to primary PCI and improved epicardial flow and tissue reperfusion. Studies are now evaluating eptifibatide in high-risk patients with non-ST elevation acute coronary syndromes (NSTE-ACS) and a planned early invasive strategy in the EARLY-ACS (Eptifibatide Administration prior to Diagnostic Catherization and Revascularization to Limit Myocardial Necrosis in Acute Coronary Syndrome) trial and in patients with primary PCI for STEMI in comparison to abciximab in the EVA-AMI (Eptifibatide versus Abciximab in Primary PCI for Acute Myocardial Infarction) trial. After the completion of these trials, the value of eptifibatide in patients undergoing PCI in different indications can be determined.     

The role of eptifibatide in patients undergoing percutaneous coronary intervention

Glycoprotein (GP) IIb/IIIa receptor antagonists inhibit the binding of ligands to activated platelet GP IIb/IIIa receptors and, therefore, prevent the formation of platelet thrombi. They have been extensively studied in patients undergoing percutaneous coronary intervention (PCI). Eptifibatide, one of the approved GP IIb/IIIa inhibitors, is a small heptapeptide that is highly selective and rapidly dissociates from its receptor after cessation of therapy. In clinical studies, concomitant administration of eptifibatide in patients undergoing elective PCI reduced thrombotic complications in the IMPACT-II (Integrilin to Minimize Platelet Aggregation and Prevent Coronary Thrombosis II) and ESPRIT (Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy) trials. In the PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) trial, which included 10,948 patients with non-ST-elevation acute coronary syndromes, eptifibatide significantly reduced the primary end point of death and non-fatal myocardial infarction at 30 days compared with placebo. In patients with ST-segment elevation myocardial infarction (STEMI), eptifibatide has been studied as adjunct to primary PCI and improved epicardial flow and tissue reperfusion. Studies are now evaluating eptifibatide in high-risk patients with non-ST elevation acute coronary syndromes (NSTE-ACS) and a planned early invasive strategy in the EARLY-ACS (Eptifibatide Administration prior to Diagnostic Catherization and Revascularization to Limit Myocardial Necrosis in Acute Coronary Syndrome) trial and in patients with primary PCI for STEMI in comparison to abciximab in the EVA-AMI (Eptifibatide versus Abciximab in Primary PCI for Acute Myocardial Infarction) trial. After the completion of these trials, the value of etifibatide in patients undergoing PCI in different indications can be determined.     

Eptifibatide: a pharmacoeconomic review of its use in percutaneous coronary intervention and acute coronary syndromes

Eptifibatide (Integrilin) is a selective inhibitor of platelet glycoprotein (GP) IIb/IIIa receptors used as adjunctive therapy for patients undergoing percutaneous coronary intervention (PCI) and for patients with acute coronary syndromes (ACS), particularly those requiring PCI. Most economic analyses of eptifibatide have incorporated clinical and healthcare resource use data from either the ESPRIT (Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy) study in low- to moderate-risk patients undergoing selective PCI with stent implantation or the PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) trial in patients with ACS. Eptifibatide achieved statistically significant reductions in combined endpoints of death and ischaemic complications in both of these large multicentre clinical trials, in which patients were randomised to receive intravenous eptifibatide or placebo as adjunctive therapy to heparin and aspirin (plus a thienopyridine in ESPRIT). In US economic analyses using ESPRIT trial data, approximately 40% and 70% of the acquisition cost of eptifibatide was offset by reduced medical resource consumption during the initial hospitalisation period and over a 1-year period, respectively. Eptifibatide was associated with a favourable cost-effectiveness ratio of $US1407 (year 2000 costs) per life-year gained (LYG) in a retrospective US cost-effectiveness analysis that incorporated data from the ESPRIT trial and modelled life expectancy using a large cardiovascular database.Several cost-effectiveness analyses used prospectively collected data from the PURSUIT trial and modelled survival projections using similar methods. These analyses, conducted in the US, Canada and Western Europe, also showed favourable results ($US3761-$US18 774 per LYG; various years of costing). Cost-utility ratios reported in US analyses varied somewhat, but remained <$US20 000 per quality-adjusted life-year gained (1996 values) when clinical efficacy data were derived from the US cohort of PURSUIT. CONCLUSION: Significant clinical benefits have been demonstrated with eptifibatide as adjunctive therapy in patients undergoing selective PCI with stent implantation in the ESPRIT trial and in patients with ACS in the PURSUIT trial. Pharmacoeconomic analyses using data from either ESPRIT or PURSUIT have demonstrated favourable cost-effectiveness ratios for both indications in various countries. ESPRIT-based results from the limited number of available economic analyses are particularly favourable. The cost-effectiveness of eptifibatide in ACS (i.e. PURSUIT-based results) may be further improved by targeting the drug for patients in whom catheterisation and PCI are planned, although further analyses are required to confirm this.     

Protection rénale: données récentes en faveur d’une nouvelle approche — l’étude PREMIER

Eptifibatide, a molecule isolated from the venom of the southeastern pygmy rattlesnake, selectively inhibits the platelet receptor IIb/IIIa. The safety and clinical efficacy of eptifibatide in patients undergoing percutaneous coronary intervention (PCI) was first evaluated in the Integrilin to Minimize Platelet Aggregation and Coronary Thrombosis (IMPACT) trial. In this study, the primary combined endpoint (composite of death, myocardial infarction [MI] or target vessel revascularization [TVR] at 30 days) occurred in 9.6% of the patients assigned to eptifibatide bolus followed by the 4-hour infusion versus 12.2% in the placebo group (p = 0.67). In the IMPACT-II trial, two different eptifibatide dosages were studied in 4011 patients undergoing elective PCI. The primary endpoint (death, MI, TVR or stent placement for threatened vessel closure at 30 days) occurred in 11.6% in the placebo group versus 9.1% in the 135/0.5 eptifibatide group (p = 0.035) and 10% in the 135/0.75 eptifibatide group (p = 0.18). The Enhanced Suppression of Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial studied a dose of eptifibatide 3- to 4-fold higher than that used in IMPACT II trial in patients undergoing non-emergent coronary artery stenting (two 180 μg/kg bolus doses 10 minutes apart). The 6-month composite endpoint (death, MI, TVR and ‘bailout’ eptifibatide use) occurred in 18.3% of patients in the placebo group versus 14.2% in the eptifibatide group (p = 0.008) and was maintained at 12 months (22.1% in the placebo group vs 17.5% in the eptifibatide group, p = 0.0068). The Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) study in 10 948 patients was designed to study the effect of eptifibatide in the treatment of acute coronary syndromes (ACS) using two different dosages (180 μg/kg bolus followed by an infusion of either 1.3 μg/kg/min or 2 μg/kg/min. The primary endpoint, a composite of death or MI at 30 days, occurred in 15.7% of placebo-treated patients and 14.2% of eptifibatide-treated patients (p = 0.042). This difference was maintained at 7 days (11.6% in the placebo group vs 10.1% in the eptifibatide group, p = 0.016) and at 30 days (15.7% in the placebo group vs 14.2% in the eptifibatide group). In the eptifibatide studies, the rates of major bleeding were 0.7% (0.5% in the control group) in ESPRIT and 2.1% (1.3% in the placebo group) in PURSUIT. The incidence of intracranial bleeding was 0.2% in ESPRIT (0.1% in the placebo group) and 0.7% in PURSUIT (0.8% in the placebo group). Significant thrombocytopenia (platelet count <20 000/μL) was reported in 0.2% of the patients receiving eptifibatide in the ESPRIT trial (0% in the placebo group) and in <1% in PURSUIT (<1% in the placebo group). In summary, several clinical trials have demonstrated a clear-cut reduction in a variety of ischemic events in patients receiving eptifibatide as adjunctive pharmacotherapy during PCI.     

Eptifibatide: a potent inhibitor of the platelet receptor integrin glycoprotein IIb/IIIa

The platelet glycoprotein (GP) IIb/IIIa integrin plays a key role in mediating platelet aggregation. Blockade of the platelet GP IIb/IIIa receptor prevents arterial thrombosis in animal models much better than does aspirin. Among the most specific inhibitors in this class of drugs is eptifibatide (Integrilin(TM), Millennium Pharmaceuticals, Inc.), a cyclic heptapeptide based on a peptide recognition sequence found in snake venom. Peptide inhibitors, such as eptifibatide, bind competitively to GP IIb/IIIa and have a short half-life, allowing the effect to be rapidly reversible and providing a favourable overall safety profile. Eptifibatide has been studied in a broad range of ischaemic coronary conditions including percutaneous coronary intervention (PCI), ST-segment and non-ST-segment acute myocardial infarction (MI) and unstable angina. In PCI and non-ST-segment MI, therapy with eptifibatide has been shown to reduce acute ischaemic complications without any increased risk of life-threatening adverse events. In the recently reported Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial, two 180 microg/kg boluses of eptifibatide, 10 min apart, followed by an 18 - 24 h infusion at 2 microg/kg/min given as adjunctive therapy in non-urgent PCI reduced the 30-day composite of death, MI and need for urgent target vessel revascularisation from 10.4 to 6.8% compared with placebo. These results were achieved under conditions of typical contemporary PCI, namely the implantation of second- and third-generation stents deployed at high balloon pressures along with modern adjunctive pharmacological treatment, particularly the universal use of thienopyridines and lower-dose heparin. Few significant pharmacological effects other than inhibition of platelet aggregation and the effect on bleeding time have been reported. Future research will focus on alternative clinical applications and combinations with other therapies to further improve cardiovascular outcomes.     

Eptifibatide: a potent inhibitor of the platelet receptor integrin glycoprotein IIb/IIIa

The platelet glycoprotein (GP) IIb/IIIa integrin plays a key role in mediating platelet aggregation. Blockade of the platelet GP IIb/IIIa receptor prevents arterial thrombosis in animal models much better than does aspirin. Among the most specific inhibitors in this class of drugs is eptifibatide (Integrilin^TMMillennium Pharmaceuticals, Inc.), a cyclic heptapeptide based on a peptide recognition sequence found in snake venom. Peptide inhibitors, such as eptifibatide, bind competitively to GP IIb/IIIa and have a short half-life, allowing the effect to be rapidly reversible and providing a favourable overall safety profile. Eptifibatide has been studied in a broad range of ischaemic coronary conditions including percutaneous coronary intervention (PCI), ST-segment and non-ST-segment acute myocardial infarction (MI) and unstable angina. In PCI and non-ST-segment MI, therapy with eptifibatide has been shown to reduce acute ischaemic complications without any increased risk of life-threatening adverse events. In the recently reported Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial, two 180 μg/kg boluses of eptifibatide, 10 min apart, followed by an 18 – 24 h infusion at 2 μg/kg/min given as adjunctive therapy in non-urgent PCI reduced the 30-day composite of death, MI and need for urgent target vessel revascularisation from 10.4 to 6.8% compared with placebo. These results were achieved under conditions of typical contemporary PCI, namely the implantation of second- and third-generation stents deployed at high balloon pressures along with modern adjunctive pharmacological treatment, particularly the universal use of thienopyridines and lower-dose heparin. Few significant pharmacological effects other than inhibition of platelet aggregation and the effect on bleeding time have been reported. Future research will focus on alternative clinical applications and combinations with other therapies to further improve cardiovascular outcomes.     

Glycoprotein IIb/IIIa receptor therapy in percutaneous coronary intervention and non-ST-segment elevation acute coronary syndromes. Estimating the economic implications

In addition to efficacy and safety, cost is an important determinant of the use of glycoprotein IIb/IIIa (GPIIb/IIIa) therapy in patients with acute coronary syndromes (ACS) or undergoing percutaneous coronary intervention (PCI). In PCI, the average procurement cost of GPIIb/IIIa therapy ranges from $US400 to $US1500 (1999 values) per patient treated, depending on agent, dose and duration of infusion. Prospective economic substudies with abciximab and tirofiban have demonstrated subsequent cost savings that partially offset the procurement costs of the agents. The drug procurement costs per death or myocardial infarction (MI) prevented in PCI appear to vary from $US10,500 to $US37,000, depending on the agent. Abciximab has been proven to provide a survival benefit in the setting of PCI, including coronary stenting. Analyses of abciximab use yield cost-effectiveness ratios of $US2875 to $US14,765 per life-year or quality-adjusted life-year saved, which compares favourably with most widely accepted therapies. In non-ST-segment elevation ACS, drug procurement costs range from $US700 to $US1700 per patient treated, also depending on agent, dose and duration of infusion. Evidence of cost offsets from changes in subsequent resource utilisation are limited and seem contingent upon a conservative risk-stratification approach. Drug procurement costs have been calculated as $US32,000 to $US82,000 per death or MI prevented in the ACS trials. Cost-effectiveness ratios of $US16,000 per life-year saved for the US and Western European cohorts in the Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trial are favourable. If these analyses prove correct, the cost effectiveness of GPIIb/IIIa receptor therapy for patients with non-ST-segment elevation ACS will also compare favourably with other widely accepted therapies in industrialised countries. More clinical and economic data are necessary to allow better selection of specific patients who will receive the most benefit from GPIIb/IIIa therapy in healthcare systems with limited resources.     

Low molecular weight heparins combined with platelet glycoprotein IIb/IIIa inhibitors in the management of acute coronary syndromes

Clinical trials of several platelet glycoprotein (GP) IIb/IIIa receptor inhibitors have demonstrated an unequivocal benefit of this potent antithrombotic therapy in high-risk patients with acute coronary syndromes (ACS) as well as in those undergoing percutaneous coronary intervention. In all of these major trials, however, GP IIb/IIIa inhibitors were used in combination with unfractionated (UF) heparin. Low molecular weight heparins (LMWH) have several advantages over UF heparin therapy, making them attractive alternatives for use in combination with GP IIb/IIIa inhibitors. In the INTegrelin and Enoxaparin Randomized assessment of Acute Coronary syndrome Treatment (INTERACT) study, combination therapy using the GP IIb/IIIa inhibitor eptifibatide (Integrilin) and the LMWH enoxaparin (Lovenox) in patients with high-risk non-ST-segment elevation ACS, resulted in improved outcomes compared to the currently recommended therapy of UF heparin, with better safety results. It is anticipated that the LMWHs may soon replace the traditional UF heparin for combination therapy with GP IIb/IIIa inhibitors in the medical stabilisation of patients with ACS. Results of other ongoing studies of LMWH combinations with other GP IIb/IIIa inhibitors and in the setting of percutaneous coronary intervention are awaited.     

Eptifibatide: a review of its use in patients with acute coronary syndromes and/or undergoing percutaneous coronary intervention

Eptifibatide, a cyclic peptide, is a highly specific, intravenously administered glycoprotein (GP) IIb/IIIa receptor antagonist. By preventing fibrinogen binding to the GP IIb/IIIa receptor, eptifibatide inhibits platelet aggregation and prevents thrombus formation. Clinically, the drug is used as an adjunct to heparin and aspirin. The PURSUIT trial, conducted in >10,000 patients with unstable angina or non-Q-wave myocardial infarction (MI), showed that eptifibatide (180 microg/kg bolus then 2 microg/kg/min infusion for < or =72 hours) reduces the 30-day risk of death or nonfatal MI, with this benefit apparent at 96 hours. The absolute reduction in this end-point of 1.5% persisted at 6 months. The drug is effective in patients undergoing percutaneous coronary intervention (PCI), and, as shown in the North American subgroup, in patients in whom medical management is appropriate. Eptifibatide is also beneficial in patients undergoing PCI, whether or not they have unstable angina or non-Q-wave MI. In a dosage of 135 microg/kg then 0.5 microg/kg/min for 24 hours, eptifibatide reduced the 30-day risk of a combined end-point (death, nonfatal MI and urgent or emergency coronary interventions) by 2.5% (absolute reduction) in patients undergoing PCI in the IMPACT-II trial, when measured by per-protocol (patients treated), but not intent-to-treat, analysis. The drug also decreased the incidence of abrupt vessel closure and ischaemic cardiovascular complications in the first 24 hours (the period of greatest risk). Bleeding episodes are the most common adverse event associated with eptifibatide therapy. Although the incidence of major bleeding is increased with eptifibatide, most bleeding episodes are minor and occur at the vascular access site. The drug is not associated with an excess of intracranial bleeds, stroke or thrombocytopenia, does not appear to increase bleeding risk in patients undergoing coronary artery bypass graft (CABG), and does not cause antibody formation. Limited data suggest that eptifibatide may improve coronary flow when combined with alteplase in patients with acute Q-wave MI, but the possibility of increased bleeding with eptifibatide plus thrombolytics should be borne in mind. CONCLUSIONS: Intravenous eptifibatide, when combined with aspirin and heparin, reduces the 30-day risk of ischaemic events in patients with unstable angina and non-Q-wave MI and decreases ischaemic cardiovascular complications at the time of greatest risk in patients undergoing PCI. With its acceptable tolerability profile eptifibatide is a suitable option as a short term adjunct in these clinical settings. Whether eptifibatide in combination with fibrolysis may improve outcome in patients with acute Q-wave MI has yet to be determined.     

Eptifibatide: a potent inhibitor of the platelet receptor integrin,glycoprotein IIb/IIIa

Platelet aggregation is intimately involved in the pathophysiology of acute coronary syndromes. Blockade of the platelet glycoprotein IIb/IIIa receptor, the mediator of platelet aggregation induced by all physiologic agonists, prevents arterial thrombosis in animal models far more effectively than aspirin. Eptifibatide (Integrilin ?) is a rapidly reversible competitive inhibitor of glycoprotein IIb/IIIa studied in a broad range of ischaemic coronary conditions, including percutaneous coronary intervention, ST-segment and non-ST-segment acute myocardial infarction and unstable angina. In each case, therapy with eptifibatide has reduced acute ischaemic complications without any increased risk of life-threatening bleeding or adverse events. Based on data from the Integrelin to Minimize Platelet Aggregation and Coronary Thrombosis (IMPACT) II study, a salutary benefit in the range of a 20 - 25% reduction in adverse clinical events can be expected in patients undergoing coronary intervention. Few significant pharmacological effects other than inhibition of platelet aggregation and the effect on bleeding time have been reported. Future research will focus on alternative doses, infusion regimens and combinations with other therapies to improve further cardiovascular outcomes.     

Pharmacoeconomics of anticoagulants in acute coronary syndrome and percutaneous coronary intervention

Economic evaluation plays an important role during almost all stages of pharmaceutical design and use. This paper reviews the recent pharmacoeconomic literature on the use of anticoagulants for acute coronary syndromes (ACS) and percutaneous coronary intervention (PCI). Both ACS and PCI are common reasons for hospitalization and contribute significantly to costs of care. ACS and PCI practice standards are still evolving. For ACS enoxaparin does appear to be more cost-effective around the globe than unfractionated heparin (UFH) when clopidrogel and glycoprotein IIb/IIIa (GP IIb/IIIa) inhibitors are not used. With the high prevalence of clopidrogel and GP IIb/IIIa use, the question may be moot. Since the cost of UFH therapy, including the cost of anticoagulant monitoring, is less expensive than enoxaparin therapy, UFH is probably the more cost-effective strategy. For PCI, as ischemic complications were reduced during the mid'90's, bleeding complications have become the most common problem and a major cost driver. Other complications that can drive costs include the occurrence of MI and revascularization procedures (repeat PCI or CABG). Results suggest that bivalirudin plus a provisional GP IIb/IIIa inhibitor is the most cost-effective strategy for patients undergoing elective PCI. There is no clear evidence regarding its use in urgent PCI. ACS and PCI practice standards are still evolving. It would be useful to embed economic studies within new clinical trials. Full economic analysis of groups at high risk for bleeding while undergoing PCI is needed.     

A review of clinical trials with eptifibatide in cardiology

Glycoprotein (GP) IIb/IIIa receptor antagonists inhibit the binding of ligands to activated platelet GP IIb/IIIa receptors and, therefore, prevent the formation of platelet thrombi. Additional antithrombin therapy should be given in connection with GP IIb/IIIa administration. Eptifibatide is a small heptapeptide, which is highly selective and rapidly dissociates from its receptor after cessation of therapy. In clinical trials (IMPACT-II and ESPRIT) concomitant administration of eptifibatide to patients undergoing percutaneous coronary intervention (PCI) reduced thrombotic complications. In the PURSUIT trial, in patients with non-ST-elevation acute coronary syndromes, eptifibatide, compared to placebo, significantly reduced the primary endpoint of death and nonfatal myocardial infarction at 30 days. In patients with STEMI eptifibatide has been studied as an adjunct to fibrinolysis and primary PCI; it improved epicardial flow and tissue reperfusion. Current studies are evaluating eptifibatide as upstream therapy in high-risk patients with NSTE-ACS, in the EARLY-ACS and in comparison with abciximab in patients with primary PCI in the EVA-AMI trial.     

Low molecular weight heparins combined with platelet glycoprotein IIb/IIIa inhibitors in the management of acute coronary syndromes

Clinical trials of several platelet glycoprotein (GP) IIb/IIIa receptor inhibitors have demonstrated an unequivocal benefit of this potent antithrombotic therapy in high-risk patients with acute coronary syndromes (ACS) as well as in those undergoing percutaneous coronary intervention. In all of these major trials, however, GP IIb/IIIa inhibitors were used in combination with unfractionated (UF) heparin. Low molecular weight heparins (LMWH) have several advantages over UF heparin therapy, making them attractive alternatives for use in combination with GP IIb/IIIa inhibitors. In the INTegrelin and Enoxaparin Randomized assessment of Acute Coronary syndrome Treatment (INTERACT) study, combination therapy using the GP IIb/IIIa inhibitor eptifibatide (Integrilin^®) and the LMWH enoxaparin (Lovenox^®) in patients with high-risk non-ST-segment elevation ACS, resulted in improved outcomes compared to the currently recommended therapy of UF heparin, with better safety results. It is anticipated that the LMWHs may soon replace the traditional UF heparin for combination therapy with GP IIb/IIIa inhibitors in the medical stabilisation of patients with ACS. Results of other ongoing studies of LMWH combinations with other GP IIb/IIIa inhibitors and in the setting of percutaneous coronary intervention are awaited.     

Optimal use of platelet glycoprotein IIb/IIIa receptor antagonists in patients undergoing percutaneous coronary interventions

Discovery of the central role of platelets in the pathogenesis of acute coronary syndromes (ACS) and ischaemic complications of percutaneous coronary interventions (PCI) has led to the widespread use of oral and parenteral platelet inhibitors to treat these conditions. Glycoprotein (GP) IIb/IIIa (also known as α(IIb)β(3)) receptors on the surface of platelets play an essential role in platelet aggregation and serve as a key mediator in the formation of arterial thrombus. When activated, GP IIb/IIIa receptors bind to fibrinogen, which serves as the 'final common pathway' in platelet aggregation. Of the numerous agents developed for modulating platelet activity, intravenous platelet GP IIb/IIIa receptor antagonists are the most potent. There are four agents in clinical use, including abciximab, eptifibatide, tirofiban and lamifiban, although lamifiban is not approved for use in the US. While all agents block fibrinogen binding to GP IIb/IIIa, they do so by different mechanisms. Abciximab is a humanized form of a murine monoclonal antibody directed against GP IIb/IIIa, eptifibatide is a synthetic, cyclic heptapeptide that contains a lysine-glycine-aspartic acid (KGD) sequence that mimics the arginine-glycine-aspartic acid (RGD) sequence found on GP IIb/IIIa, tirofiban is a non-peptide antagonist derived by optimization of the tyrosine analogue that structurally mimicks the RGD-containing loop of the disintegrin echistatin, and lamifiban is a synthetic, non-cyclic, non-peptide, low-molecular-weight compound. In clinical trials, use of these agents reduces ischaemic adverse cardiovascular events in patients with ACS undergoing PCI, but at a cost of increased bleeding.     

Bleeding associated with eptifibatide targeting higher risk patients with acute coronary syndromes: incidence and multivariate risk factors

The objective of this study was to determine the safety of the glycoprotein IIb/IIIa receptor inhibitor eptifibatide in patients at high risk for adverse clinical outcomes and to determine risk factors for eptifibatide-associated bleeding. Consecutive patients (n = 175) who presented with an acute coronary syndrome and who were at high risk for adverse clinical outcomes were prospectively observed for eptifibatide-associated bleeding, which was classified according to Thrombolysis in Myocardial Infarction (TIMI) and Global Use of Strategies to Open Occluded arteries (GUSTO) criteria. High risk was defined as unstable angina or non-Q-wave myocardial infarction with at least one of the following: left ventricular ejection fraction < 40%, diabetes mellitus, ST segment depression or transient ST segment elevation, serum [troponin I] > 2.5 ng/mL, and recurrent angina symptoms after initiation of conventional antianginal therapy. Bleeding incidences in the patients in this study were compared with those in the 4722 eptifibatide-treated patients in the Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trial. Compared to PURSUIT patients, the population in this study was similar in age but had a higher proportion of females, African Americans, hypertension, diabetes, prior myocardial infarction, heart failure, and revascularization. Bleeding incidences in this study's patients were similar to or lower than those in the PURSUIT population: TIMI major 1.1% versus 10.8%, TAMI minor 12.6% versus 13.1%, GUSTO severe 1.7% versus 1.5%, GUSTO moderate 3.9% versus 11.3%, and GUSTO mild 19.7% versus 26.1%. Renal dysfunction was an independent risk factor for TIMI (odds ratio = 9.1 ([95% CI= 1.6-52.5]) and GUSTO (odds ratio = 6.1 [95% CI = 1.2-30.0]) bleeding. In conclusion, despite being at higher risk for adverse outcomes, patients administered eptifibatide according to this study's institutional guidelines had comparable or lower bleeding rates than in the PURSUIT trial. Renal dysfunction is an independent risk factor for eptifibatide-induced bleeding.     

Combination of low molecular weight heparins with antiplatelet agents in non-ST elevation acute coronary syndromes: an update

This article reviews the use of low molecular weight heparin (LMWH) and antiplatelet agents in the treatment of unstable angina and non-ST segment elevation myocardial infarction (NSTEMI), which together account for 1 million hospitalisations annually in the US alone. Mortality and recurrent myocardial infarction (MI) in these conditions is currently approximately 8 to 16% at 1 month, and there is a need to optimise treatment further. Since their introduction, LMWHs have been shown to be successful and well tolerated in the treatment of unstable angina and NSTEMI, but differences have been seen in their efficacy compared with the parent compound, unfractionated heparin (UFH). A meta-analysis of all LMWHs, grouped, versus UFH showed equivalent efficacy and safety. The LMWHs dalteparin sodium and nadroparin calcium have independently been shown to be as effective as UFH. However, enoxaparin sodium has been shown to have greater clinical efficacy than UFH in patients with unstable angina (UA)/NSTEMI. One area of new research is patients with UA/NSTEMI who later undergo percutaneous coronary interventions (PCI), and early data suggest enoxaparin can be safely used as an anticoagulant instead of UFH in these patients. There is a wealth of data for glycoprotein (GP) IIb/IIIa receptor antagonists (abciximab, eptifibatide, lamifiban, and tirofiban), although some are conflicting. Recent meta-analyses suggest that some benefit is conferred by using these compounds, particularly in patients who undergo PCI. Recent trials have focussed on combining GP IIb/IIIa antagonists with LMWH, and although data is still scant, the ACUTE (Anti-thrombotic Combination Using Tirofiban and Enoxaparin) and ACUTE II studies indicate the safety and potential clinical benefit of combining enoxaparin with tirofiban in patients with UA/NSTEMI not undergoing PCI, compared with UFH and tirofiban. The NICE (National Investigators Collaborating on Enoxaparin) 4 study collected data on the combination of enoxaparin and abciximab in patients undergoing PCI, and both safety and efficacy data compared well with historical data collected on the use of UFH with abciximab. The more recent NICE 3 study extended this finding to the combination of enoxaparin with abciximab, tirofiban or eptifibatide. The safety of two doses of dalteparin and abciximab had also been investigated, with the higher dose the efficacious, and also with safety, in patients undergoing PCI. In addition, a GUSTO (Global Use of Strategies to Open Occluded Coronary Arteries in Acute Coronary Syndromes) IV substudy found that dalteparin had equivalent safety to UFH when co-administered with abciximab in patients not undergoing PCI. The NICE 3 and 4 trials were not randomised comparisons, and as such there results must be interpreted with caution. Recently, the CRUISE (Coronary Revascularisation Utilizing Integrelin [eptifibatide] and Single-bolus Enoxaparin) and INTERACT (Integrelin and Enoxaparin randomised assessment of Acute Coronary Syndromes Treatment) studies have provided evidence for both the safety and efficacy of enoxaparin combined with eptifibatide in non-ST elevation patients with acute coronary syndromes. A further study (SYNERGY [Superior Yield of the New strategy of Enoxaparin, Revascularization and GlYcoprotein IIb/IIIa inhibitors]) will investigate the efficacy of the combination of enoxaparin with abciximab versus that of UFH and abciximab in a large cohort of 8000 patients. The use of GP IIb/IIIa agents and LMWH in patients with UA/STEMI has led to their use in those with ST-elevation MI, and studies indicate LMWH is efficacious and can be used safely as an adjunct to thrombolysis. New studies will investigate the use of these agents in patients with STEMI not undergoing thrombolysis and we await the results of these studies.     

Platelet glycoprotein IIb/IIIa inhibitors in percutaneous coronary intervention: focus on the pharmacokinetic-pharmacodynamic relationships of eptifibatide

Eptifibatide is a truncated derivative of the naturally occurring rattlesnake venom protein known as barbourin. It is a cyclic heptapeptide that mimics the tertiary structure found in the parent compound which allows it to bind receptors with the KGD (Lys-Gly-Asp) peptide recognition sequence. Specifically, eptifibatide is a competitive antagonist for the activated platelet glycoprotein IIb/IIIa receptor. Its mechanism of action involves preventing the binding and cross-linking of fibrinogen to the platelet surface. This binding site for fibrinogen is associated with five Ca2+ ions that help maintain the tertiary structure of the receptor and affect the affinity of other ligands such as eptifibatide.Arterial injury induced by percutaneous coronary interventions (PCI) such as balloon angioplasty and stenting, and the spontaneously occurring disease process known as the acute coronary syndrome (ACS), share a common underlying pathophysiology. In both situations, disruption of integrity of the arterial wall initiates a cascade of platelet activation, adhesion and aggregation. Ultimately, this process may proceed to arterial thrombosis unless controlled or modified. Advances in understanding how the platelet plays a pivotal role in this process have significantly enhanced therapy for patients with ACS and have resulted in important reductions in thrombotic complications from PCI procedures. Central to these advances has been evolving understanding of platelet-inhibiting pharmaceutical agents such as eptifibatide. The development of a rational administration regimen for eptifibatide parallels the growth in the understanding of the underlying mechanisms of platelet receptor functions. The binding of eptifibatide to the receptor involves displacement of receptor-associated Ca2+ from the activated binding site. Early in the clinical development of eptifibatide, this was poorly appreciated and resulted in an underestimation of the appropriate doses for this agent. Through a series of small clinical trials and laboratory studies, deficiencies in the early administration regimens were identified and a more effective dose schedule was determined. Modelling of the drug based on its two-compartment pharmacokinetics further defined the role of a newer double-bolus initiation of therapy verses the original single-bolus approach. In a large-scale clinical trial using this double-bolus followed by infusion regimen in PCI procedures, clinical efficacy was shown to be significantly improved over placebo and the earlier, low-dose regimens used in the original trials of eptifibatide.     

Intracoronary use of GP IIb/IIIa inhibitors in percutaneous coronary interventions

The glycoprotein (GP) IIb/IIIa receptor is critical to the process of platelet aggregation and thrombus formation as it serves as the final common pathway for platelet aggregation. For this reason, the development of GP IIb/IIIa inhibitors that block fibrinogen binding to the receptor has become an attractive strategy for antiplatelet therapy with an expected strong and specific effect. Presently, there are three commercially available GP IIb/IIIa inhibitors: abciximab, eptifibatide and tirofiban. All three drugs are commonly administered intravenously, and large-scale clinical trials have demonstrated a clear clinical benefit and good safety profile in patients at high risk, especially those undergoing percutaneous coronary interventions (PCI). Recently, several studies tested the intracoronary (IC) route for GP IIb/IIIa inhibitors in order to verify its safety and its possible superiority as compared to the intravenous (IV) route. The majority of the studies testing the IC route were conducted using abciximab and in patients with STEMI with better results in terms of myocardial reperfusion and infarct size and also promising results in terms of clinical outcome. On the IC administration of eptifibatide and tirofiban only some, even if promising, data are available. Larger and randomized studies are warranted to confirm the superiority of the IC route of administration of the GP IIb/IIIa inhibitors to the IV one in patients with coronary artery disease undergoing PCI.     

依替巴肽与替罗非班在ACS介入治疗中有效性和安全性

目的 探讨依替巴肽与替罗非班在急性冠状动脉综合征(ACS)介入治疗中的临床疗效和安全性.方法 ACS中不稳定型心绞痛及非ST段抬高心肌梗死(UA/NSTEMI)28例,按就诊顺序随机分为依替巴肽(受试)组和替罗非班(对照)组,在常规予抗血小板及抗凝治疗基础上,经皮冠状动脉介入治疗(PCI)手术开始时即静脉予依替巴肽或替罗非班,观察比较两组住院期间及术后30 d主要不良心脏事件(MACE)、出血情况及血小板减少症.结果 两组住院期间及术后30 d内MACE事件均末发生;24 h心电图缺血导联数与用药及PCI前相比均减少,对照组更明显(P＜0.05);两组均未发生大出血事件,轻微出血发生率受试和对照分别为21.4%和28.6%.结论 两种血小板膜糖蛋白受体拈抗剂在ACS介入治疗中均能起到辅助作用,且安全性好,但长期疗效及毒副作用有待进一步研究观察.     

Eptifibatide: a potent inhibitor of the platelet receptor integrin, glycoprotein IIb/IIIa

Platelet aggregation is intimately involved in the pathophysiology of acute coronary syndromes. Blockade of the platelet glycoprotein IIb/IIIa receptor, the mediator of platelet aggregation induced by all physiologic agonists, prevents arterial thrombosis in animal models far more effectively than aspirin. Eptifibatide (Integrilintrade mark) is a rapidly reversible competitive inhibitor of glycoprotein IIb/IIIa studied in a broad range of ischaemic coronary conditions, including percutaneous coronary intervention, ST-segment and non-ST-segment acute myocardial infarction and unstable angina. In each case, therapy with eptifibatide has reduced acute ischaemic complications without any increased risk of life-threatening bleeding or adverse events. Based on data from the Integrelin to Minimize Platelet Aggregation and Coronary Thrombosis (IMPACT) II study, a salutary benefit in the range of a 20 - 25% reduction in adverse clinical events can be expected in patients undergoing coronary intervention. Few significant pharmacological effects other than inhibition of platelet aggregation and the effect on bleeding time have been reported. Future research will focus on alternative doses, infusion regimens and combinations with other therapies to improve further cardiovascular outcomes.